Automatically folding boom for cranes



Jan. 15, 1963 L. THOMAS 3,073,457

AUTOMATICALLY FOLDING BOOM FOR CRANES Filed March 10, 1960 INVENTOR Z 00/5 Thomas ATTOR NEYS AUTOMATICALLY FOLDING BOOM F GRCRANES Louis Thomas, 32 Rue de Nantes, Chantonnay, France Filed Mar. 10, 1960, Ser. No. 14,103 Claims priority, application France Apr. 28, 1959 6 Claims. (Cl. 212-144) In order tolpermit cranes larger than a certain size to be transported, and particularly those which are mounted on an automotive vehicle, itis necessary to solve the problem of reducing'its maximum dimensions, both height and length, so that it canlbe moved by. highway or railway.

T o avoid removing the boom, which is impractical and rather dangerous, the boom is usually pivotally attached to the base of the cab, so that it may be lowered for transport by means of a supplemental cable independent of the load litting cable, and raised again to one or more angular working positions which correspond to decreasing reaches and increasing lifting powers. Be that as it may, with truck carried cranes so equipped, it is necessary during travel along a highway either to position the boom toward the rear with respect to the direction of movement, which considerably increases the overall length of the vehicle and makes turning difiicult, or-

to lower it toward the front in a nearly horizontal direction, which usually means that it must be positioned along side of the cab, which is then usually reduced to a very small enclosure of special construction, which is very expensive and rather uncomfortable. Moreover, in this case, the unsymmetrical position of the boom renders control difficult and, particularly during turns from the side opposite the boom, interferes with visibility and represents a real hazard to the driver in case of an accident.

The present invention is intended to eliminate these inconveniences, while retaining the advantage of a crane which is always ready for immediate use.

The object of the present invention is to provide a new article of manufacture which consists of a-crane having an angularly adjustable boom, characterized by the fact that the boom comprises two pivotally connected parts, the lowermost of which is also pivotally connected to the base of the cab of the crane, while theupper part may be folded back so as to assume asubstantially horizontal position passing over the drivers cab of the truck.

In a preferred embodiment of the invention, the folding and unfolding of this jointed boom is brought about by means of the normal lifting cables of the boom. The effective power of these cables for lifting the upper part of the boom is multiplied, if necessary, by means of a 11 and passes over the pulley 12 before being wound up on the winchinside the cab 3. As arule, the traction.

pulley system comprising one or more auxiliary cables connected to one or more of the boom lifting cables and working through a supplementary set of them during lowering of the upper part.

In order that the invention may be better understood, two representative embodiments thereof will now be de scribed, purely by way of illustration, and without limiting the scope of the invention to the specific details thereof. These are shown in the accompanying drawings in which:

FIG. 1 shows a truck type crane in accordance with by means of a joint or hinge 7 at the lower side of the boom. a

'When travelling,"the joint 7 rests on a rear support Stand the. upper part 6 of the boom rests approximately horizontally on a front support 9. The support 8 may be replaced by a rod, a'cable or a chain limiting the inclination of the part 5, for example, by connecting th hinge 7 to the crane cab 3.

In order to raise the upper part of the boom 6 so as to bring. it into alignment with the lower part 5, one would naturally expect to simplypull on the boom lifting cable 10 which is attached to the end of this boom at of this cable 10 is insufiicient for this purpose because the pivot point 7 is too nearthe line 11-12 along which the force is applied, so-that the torque is very low. The distance between the point 7 and the cable may be increased by providing second pulley 13 carried by anarm 14 mounted, for example on the lower part 5, but this is not usually sufficient. v

To greatly increase the effective torque acting to swing the part 6 about the pivot point 7 without increasing the tension on the cable 10, a second cable 16 is-attached to the first at the point 15 and reeved into a pulley arrangement having as many loops as required between a pulley block 17 near the end 11 of the boom and a pulley block 1 8 fixed to the end of the arm 14.

However, in order to avoid unduly elongating this cable 16, the successive loops in excess of three are passed around-a pulley 19 fixed to the end of the arm 20 mounted on the upper part 6 of the boom, nearer to the pulley 18 than is the pulley 17.

In the embodiment shown on FIGS. 1 and 2, the cable 16 runs from the point 15 successively over the pulleys 17, 18 and 19 and is attached at the point 21 to the arm 14, thus creating a pulley system having four loops which multiplies by four the force exerted by the cable 10.

The operation of this device is clearly shown on FIGS. 1 and 2.

It will be seen from FIG. 1 that the part of the cable '10 between the junction point 15 andthe attachment point 11 is slack so that when cable 10 is pulled, the tension on this cable is transmitted only to cable 16, the force exerted by this cable is multiplied four times by the pulley system, as hereinbefore indicated, and lifts the upper part 6 of the boom without difficulty until it is brought into alignment with the part 5. I

The apparatus is controlled, as seen on FIG. 2, in such a manner thaat when this alignment of the two articulated parts of the boom has been accomplished, the part "of the.

abutment against the upper'end of the lower part 5, and

the entire boom 56 rises from the position shown on Fit 2, so that the joint 7 is lifted off the support 8, after which the cab of the crane may turn about itsvertical axis so as to position the boom in any desired direction for use. In such a direction, since the support 8 is no longer opposite the joint 7, it will readily be seen that the boom may be either raised or lowered from the position shown in FIG. 2, and in any case, the force exerted through the lifting cable 1% will be transmitted directly between the pulley 12 and the attachment point 11, as in the case of a conventional liftable boom, the cable 16 having practically no elfect.

. 3.0- 157115 "Patented Jan.15,' 19 3 f It is equally .clear that its lower end supported by the vehicle and its upper end supported by. the cable, its'own weight resists any tendency for the adjacent ends of the upper and lower boom parts to rise sufi'iciently to permit bending at the joint 7. In any event, if such a pivoting begins to take place, this immediately results in an increase in the tension of the cable 16 which, when multiplied by the pulley system, as previously indicated, positively opposes any bending. However, it is possible to add a quick acting locking means between parts and 6, if desired.

On the other hand, When the boom of the crane is brought intothe position shown in 'FIG. 2, the joint 7 rests on the support 8 when'the cable 10 is released. In this case, and in this case only, the boom folds up autowhen theboorn is in use, with.

matically if the cable 10 continues to be paid out, but

moves slowly due to the speed ratio introduced by the pulley system.

In a variation of the preceding. embodiment, the support Sinay be replaced by one or two removable cables connecting the point 7 to the cab of the crane 3.

FIG. 3 shows another embodiment of the invention. useful in the common case in which the lifting cable is attached, at its two ends, to the two points 11 at the end of the boom, and passes over a pulley wheel 22 equalizing the tensions of the two loops created thereby. Moreover, the pulling force on the pulley 22 is obtained from the winch in the cab by means of a pulley system 23. The lifting force exerted on the loops of the cable 10 is usually more than required, at least as long as the boom is not carrying any load, and in this case it is often sufiicient to provide two cables 16, similar to those just described, connected at two points 15, each to one of the loops of the cable 10, passing over two pulleys 17, near the points 11 and attached at two points 21 to the end of the arm 14 similar to the arm just described. This arrangement simply multiplies by two the effective force between 17 and 21. In order to equalize the tensions on the cables 16, they may be replaced by a single cable formed into two loops, while replacing the attaching points 21 with dividing pulleys.

It is obvious that the drawings are essentially schematic and intended primarily to make it easy to follow the paths of the cables. In practice, it would be desirable to locate the pulleys 13 and 1S and the point 21 as close as possible to the end of the arm 14, that is to say, to position them on the same horizontal axis, whereas the length of the arm 20 should be such that the pulley 19 is at the same height.

What has hereinbefore been said with respect to a truck mounted crane applies to other types as well, especially to tractor mounted cranes which are to be transported on a trailer or goose-necked semi-trailer. The boom in this case is folded exactly as hereinbefore de scribed, over the tractor cab, the supports 8 and 9 being fixed on the trailer or semi-trailer.

It will be appreciated that the embodiments hereinbefore described have been given purely by way of example and that the invention is in no way limited to these specific embodiments but may be modified as to details without thereby departing from the spirit of the invention.

ln particular, in the embodiment of FIG. 1, the number of loops of the pulley system of the cable 16 may be tnade equal to any whole number desired, instead of four, by increasing (or decreasing), if necessary, the number of pulleys 18 and 19, and shifting the attaching point 21 to the support 29, as required, for an odd number of loops.

It is also possible to attach to the cable or cables 16 shown in FIG. 3 a pulley system having more than two loops.

Finally it would be possible to reduce the length of the portion of the boom which projects beyond the vehicle by sliding the part 6 on the support 9 by means of rollers or the like, the part 5 coming to rest against the cab. To produce this movement it is sufficient to, lower the boom as before, and then, after having slackened the cable 19, to connect the oint 15 :0 the point 11 by means of ,a hook, for example, and then pull on the cable 10 or start up the winch after the book has been attached to the boom. The weight of the members 5 and 6 themselves should be sufficient to return them to the forward position, but this may be supplemented by auxiliary means.

Upon release of the cable winch and actuation of the winch controlling the boom, the lower part of the boom is inclined to return to the position indicated on P162. l, thus moving forward the part 6. The part 6 is then brought into working position as shown in FIG. 2. These operations are carried out in a smooth succession, without requiring any abnormal efifort or the mounting or dismounting of any element.

What I claim is:

1. A crane of the type comprising a vehicle, a boom pivotally mounted on said vehicle for swinging movement in a vertical plane, said boom being divided into upper and lower parts, a pivotal connection joining said upper and lower parts, means for supporting said lower boom part in a predetermined angular position, a winch mounted on said vehicle, a cable connected between said winch and the upper tip of said upperboom part, with guide means for said cable being positioned between said winch and boom tip and vertically spaced above said pivotal connection, to increase the effective lifting component exerted on said boom tip when tension is applied to said cable by said winch, said upper boom part being provided with pulley means near its upper tip, and both said upper and lower boom parts carrying upwardly projecting lever arms near their adjacent ends, both of said arms carrying pulley means, said cable comprising a main line fixed to said boom tip and an auxiliary line connected to said main line intermediate said Winch and boom tip, said auxiliary line then passing successively over the pulley means on said boom tip, the pulley means on the arm projecting upwardly from said lower boom part, and the pulley means on the arm projecting upward from said upper boom part, and being attached at its end to the arm on said lower boom part.

2. A crane as claimed in claim 1 in which said lever arms are mounted to swing apart as said upper boom part is lowered at an angle to said lower boom part, thereby drawing the point on said main line at which it is attached to said auxiliary line closer to the free end of said upper part and causing the portion of said main line therebetween to become slack.

3. A crane of the type comprising a vehicle, a boom pivotally mounted on said vehicle for swinging movement in a vertical plane, said boom being divided into upper and lower parts, a pivotal connection joining said upper and lower parts, means for supporting said lower boom part in a predetermined angular position, a winch mounted on said vehicle, a cable connected between said winch and the upper tip of said upper boom part, with guide means for said cable being positioned between said winch and boom tip and vertically spaced above said pivotal connection, to increase the effective lifting component exerted on said boom tip when tension is applied to said cable by said winch, said upper boom part being provided with first pulley means near its upper tip, an upwardly projecting lever arm being mounted on said lower boom part, second pulley means and said guide means being carried by said lever arm, and said cable comprising a main line fixed to said boom tip and an auxiliary line reeved between said first and second pulley means, said auxiliary line being attached to said main line at a point intermediate said winch and boom tip such that said auxiliary line must be drawn up suificiently to bring said upper boom portion into alignment with said lower boom portion before traction can be applied by said winch to the portion of said main line between said attachment point and said boom tip.

4. A crane of the type comprising a vehicle, a boom pivotally mounted on said vehicle for swinging movement in a vertical plane, said boom being divided into upper and lower parts, a pivotal connection joining said upper and lower parts, means for supporting said lower boom part in a predetermined angular position, a winch mounted on said vehicle, a cable connected between said rwinch and the upper tip of said upper boom part, with guide means for said cable being positioned between said winch and boom tip and vertical-1y spaced above said pivotal connection, to increase the effective lifting component exerted on said boom tip when tension is applied to said cable by said winch, said cable means comprising a main cable and auxiliary cable means, a movable pulley wheel connected to be moved by said winch, said main cable being bent about said movable pulley wheel into two laps, the ends of which are attached to said boom tip, fixed pulley wheels mounted on said boom tip, and an upwardly projecting lever arm mounted on said lower boom part and carrying said guide means, said auxiliary cable means comprising two parts, each of which is connected to said lever arm, passes around one of said fixed pulley wheels and is attached to one lap of said main cable at a point intermediate said fixed pulley wheel and bottom tip.

5. A crane as claimed in claim '4 in which a pulley wheel is carried by said lever arm and said two auxiliary cable parts form a single continuous line connected to said lever arm by being passed around the pulley wheel thereon.

6. A crane of the type comprising a vehicle, a boom pivotally mounted on said vehicle for swinging movement in a vertical plane, said boom being divided into upper and lower parts, a pivotal connection joining said upper and lower parts, means for supporting said lower boom part in a predetermined angular position, a winch mounted on said vehicle, a cable connected between said winch and the upper tip of said upper boom part, with guide means for said cable being positioned between said winch and boom tip and vertically spaced above said pivotal connection, to increase the effective lifting component exerted on said boom tip when tension is applied to said cable by said winch, pulley means carried by each of said boom parts, said cable comprising a main line extending directly from said guide means to said boom tip and an auxiliary line connected at one end to said main line at a point between said Winch and boom tip, said auxiliary line being reeved between the pulley means on said lower boom part and the pulley means on the upper boom part and attached at its other end to one of said boom parts, and the pulley means carried by one of said parts being mounted on an arm extending transversely away from that boom part.

References Cited in the file of this patent UNITED STATES PATENTS 2,649,219 Marchese Aug. 18, 1953 2,722,319 Stokes Nov. 1, 1955 2,809,756 Bannister Oct. 15, 1957 

1. A CRANE OF THE TYPE COMPRISING A VEHICLE, A BOOM PIVOTALLY MOUNTED ON SAID VEHICLE FOR SWINGING MOVEMENT IN A VERTICAL PLANE, SAID BOOM BEING DIVIDED INTO UPPER AND LOWER PARTS, A PIVOTAL CONNECTION JOINING SAID UPPER AND LOWER PARTS, MEANS FOR SUPPORTING SAID LOWER BOOM PART IN A PREDETERMINED ANGULAR POSITION, A WINCH MOUNTED ON SAID VEHICLE, A CABLE CONNECTED BETWEEN SAID WINCH AND THE UPPER TIP OF SAID UPPER BOOM PART, WITH GUIDE MEANS FOR SAID CABLE BEING POSITIONED BETWEEN SAID WINCH AND BOOM TIP AND VERTICALLY SPACED ABOVE SAID PIVOTAL CONNECTION, TO INCREASE THE EFFECTIVE LIFTING COMPONENT EXERTED ON SAID BOOM TIP WHEN TENSION IS APPLIED TO SAID CABLE BY SAID WINCH, SAID UPPER BOOM PART BEING PROVIDED WITH PULLEY MEANS NEAR ITS UPPER TIP, AND BOTH SAID UPPER AND LOWER BOOM PARTS CARRYING UPWARDLY PROJECTING LEVER ARMS NEAR THEIR ADJACENT ENDS, BOTH OF SAID ARMS CARRYING PULLEY MEANS, SAID CABLE COMPRISING A MAIN LINE FIXED TO SAID BOOM TIP AND AN AUXILIARY LINE CONNECTED TO SAID MAIN LINE INTERMEDIATE SAID WINCH AND BOOM TIP, SAID AUXILIARY LINE THEN PASSING SUCCESSIVELY OVER THE PULLEY MEANS ON SAID BOOM TIP, THE PULLEY MEANS ON THE ARM PROJECTING UPWARDLY FROM SAID LOWER BOOM PART, AND THE PULLEY MEANS ON THE ARM PROJECTING UPWARD FROM SAID UPPER BOOM PART, AND BEING ATTACHED AT ITS END TO THE ARM ON SAID LOWER BOOM PART. 